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Title: Application of x-ray absorption fine structure (XAFS) to local-order analysis in Fe-Cr maghemite-like materials

The maghemite-like oxide system γ-Fe{sub 2-x}Cr{sub x}O{sub 3} (x=0.75, 1 and 1.25) was studied by X-ray absorption fine structure (XAFS) and by synchrotron radiation X-ray diffraction (XRD). Measurements were performed at the Stanford Synchrotron Radiation Lightsource at room temperature, at beamlines 2-1, 2-3 and 4-3. High-resolution XRD patterns were processed by means of the Rietveld method. In cases of atoms being neighbors in the Periodic Table, the order/disorder degree of the considered solutions is indiscernible by “normal” (absence of “anomalous scattering”) diffraction experiments. Thus, maghemite-like materials were investigated by XAFS in both Fe and Cr K-edges to clarify, via short-range structure characterization, the local ordering of the investigated system. Athena and Artemis graphic user interfaces for IFEFFIT and FEFF8.4 codes were employed for XAFS spectra interpretation. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure (XANES) transitions were performed. By analysis of the Cr K-edge XANES, it has been confirmed that Cr is located in an octahedral environment. Fitting of the extended X-ray absorption fine structure (EXAFS) spectra was performed under the consideration that the central atom of Fe is allowed to occupy octa- and tetrahedral positions, while Cr occupies only octahedral ones. Coordination number of neighboring atoms,more » interatomic distances and their quadratic deviation average were determined for x=1, by fitting simultaneously the EXAFS spectra of both Fe and Cr K-edges. The results of fitting the experimental spectra with theoretical standards showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO{sub 3})« less
Authors:
; ;  [1] ;  [2]
  1. Centro de Investigación en Materiales Avanzados, Chihuahua, 31136, México (Mexico)
  2. Universidad Autónoma de Chihuahua, Chihuahua, 31000, México (Mexico)
Publication Date:
OSTI Identifier:
22488685
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1671; Journal Issue: 1; Conference: 11. international symposium on radiation physics, Ciudad Juarez (Mexico), 4-6 Mar 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION SPECTROSCOPY; ATOMS; CATIONS; CHROMATES; CONCENTRATION RATIO; COORDINATION NUMBER; FINE STRUCTURE; INTERATOMIC DISTANCES; INTERFACES; IRON COMPOUNDS; RESOLUTION; SYNCHROTRON RADIATION; TEMPERATURE RANGE 0273-0400 K; VACANCIES; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY